Xerographic fusing method



p 8, 1964 u. IWERKS 3,148,078

XEROGRAPHIC FUSING METHOD Original Filed July 29, 1957 2 Sheets-Sheet 1 IN VEN TOR.

us IWERKS ATTORNEY Sept. 8, 1964 u. IWERKS XEROGRAPHIC FUSING METHOD Original Filed July 29, 1957 2 Sheets-Sheet 2 i 37 49 IO 1' O 2 2 2| 24 23 3 a O FIG. 3

FIG. 4

INVENTOR.

UB IWERKS A TTOR/VEK United States Patent 3,148,678 XERGGRAPEHC FUSING METHGD Uh Iwerks, Sherman Uaks, Califi, assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Original application .Iuly 2?, 1957, Ser. No. 674,777, now Patent No. 3,049,810, dated Aug. 21, 1962. Divided and this application Dec. 11, 1961, Ser. No. 158,447

1 Claim. (Cl. 117-21) This invention relates to the field of xerography and, particularly, to an improved method for fixing xerographic powder images on support surfaces.

More specifically, the invention relates to an improved method for vapor fixing xerographic powder images having a soluble resin component wherein a powder image on a support surface is exposed to a controlled quantity of the vapor of a solvent for the resin component of the developing material of which the image is formed, whereby the solvent vapor condenses on the powder particles of the powder image and tackifies or plasticizes them to fix them to the support surface. By way of illustration, the method of the invention is disclosed in conjunction with an apparatus for generating an atmosphere of solvent vapor, temporarily maintaining the Vapor in a confined space, and applying the confined solvent vapor to the support surface on which the xerographic powder image is formed. Such an apparatus is disclosed in my copending application Serial No. 674,777, filed July 29, 1957, now Patent No. 3,049,810, of which this application is a division.

In the process of xerography, for example, as disclosed in Carlson Patent 2,297,691, issued October 6, 1942, a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its service and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the light intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductiv layer. Development of the latent image is effected with an electrostatically charged, finely divided material such as an electroscopic powder that is brought into surface contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic powder image is usually transferred to a support surface to which it may be fixed by any suitable means.

In the Carlson patent, it is noted that a variety of types of finely divided electroscopic powders may be employed for developing electrostatic latent images. However, as the art of xerography has progressed, it has been found preferable to develop line copy images with a powder formed of any of a variety of pigmented resins that have been specifically developed for the purpose. A number of such developing materials are manufactured and marketed by Xerox Corporation, of Rochester, New York, and are specifically compounded for producing dense images of high resolution and to have characteristics to permit convenient storage and handling.

Such developing materials are specifically designed to permit them to be fixed to support surfaces either by conventional heat fixing or vapor fixing techniques, in accordance with the particular application in which they are employed. However, in order to provide the characteristics mentioned above, such materials are inherently limited in latitude in the operating conditions under which they may be used. For example, in xerographic systems embodying heat fixing apparatus, the support surface on which Xerographic powder images are formed is placed in an ovenlike structure that is maintained at a constant temperature that is determined by the fusing temperature of the resin component of the xerographic developing material. Should the oven temperature be decreased, the powder images may not be properly fixed and are then subject to smearing. In the event the oven temperature is increased, the support surface itself is subjected to increased heat that is liable to deform, discolor, or even char it, depending upon the type of material of which the support surface is composed.

Similarly, in xerographic systems embodying vapor fixing apparatus, the support surface on which the xerographic images are formed is usually passed into a vapor chamber containing a saturated atmosphere of solvent for the resin component of the developing material. In such machines, it is also essential that the time of exposure to the solvent vapor be controlled in order to minimize the possibility of underfixing or overfixing the powder images, or of excessively wetting the support surface with condensed solvent. In addition, since substantially all solvents suitable for fixing xerographic powder images are either inflammable or noxious, the vapor dragout caused by the support surface moving out of the fixing apparatus tends to produce undesirable ambient conditions.

in certain applications of xerographic techniques, the matter of fixing the powder image to a support surface is a highly critical procedure and requires the employment of special methods and apparatus to effect its proper accomplishment. A typical example of such a situation occurs in the application of xerographic techniques to the production of animated cartoons.

In general, to make a cartoon movie, each frame of the finished film is exposed to a group of four or more cellulose acetate transparencies, upon which are drawn and painted the various figures in the cartoon. Usually, each transparency or cel is employed to depict a single character and a progression of cels are necessary to portray the successive movements required to simulate motion in the finished film. Sometimes a drawing may appear on only one of the cels that are being photographed, but in all cases in a given film sequence a uniform number of cels are stacked together before exposure in order to maintain consistentcy of light transmission and reflection. Background scenes are usually painted on one of several types of artist painting boards and may be painted in watercolor, tempera color, or an oil color, and are positioned in back of the cels being photographed.

Prior to the application of xerographic techniques to the production of cartoon movies, the preparation of the individual cels required that an artist draw a pencil sketch of the desired figure on heavy white bond paper in exact registration for the scene to be portrayed. The paper employed was especially prepared with a series of holes punched along one edge which were used for alignment and registration purposes. When the drawing was completed, it was passed on to a tracer who placed a cellulose acetate cel having similar registration holes over the original drawing and copied all the pencil lines of the original sketch with pen and ink. The inked drawing was then passed to another artist who colored the ink outlines on the reverse side of the cel, according to a predetermined coloring sketch. After the painting was completed, the several cels required to form a particular scene were mounted on a board, using the holes to achieve proper registration, and were photographed to form a single frame of the movie.

Since normal motion picture projection speeds are twenty-four frames per second and at least four cels are required to be prepared for each frame, it is apparent that a full minute of projection requires the preparation of many thousands of cels and that the preparation of a two-reel short requires the expenditure of a tremendous amount of effort. In addition, since highly skilled artists are required for this work, it is obvious that the cost of making animated cartoons is quite high. In

order to decrease these costs, it was found that xerographic techniques could be employed to eliminate a substantial portion of the skilled manual craftsmanship that was previously employed. Specifically, it was found that xerocopies of the original artist sketches could be transferred directly to cels and fused thereon, thereby eliminating completely all of the manual tracing previously required. In addition, it was found that certain of the artistss shading effects, that were normally lost in the manual tracing operation, could be retained by the careful application of xerographic techniques to improve the quality of the finished cartoon.

In practice, this is effected by uniformly charging a photoconductive layer formed on a conductive backing, exposing the charged photoconductor to the sketch required to be reproduced, developing the latent electrostatic image of the sketch formed on the photoconductive layer with a xerographic developing material including a soluble resin component, transferring the xerographic powder image thus formed to the surface of a cellulose acetate cel and fixing the powder image on the cel surface. Obviously, heat fixing cannot be employed in such a technique since the heat of the fixing oven would distort, if not destroy the cel material. Since vapor fixing is commonly employed with cellulose acetate material in xerographic applications, vapor fixing is the obvious solution. However, since an overexposure of a cellulose acetate film to solvent vapor frequently results in fogging of the film as a result of the residual film of solvent left on the film after fixing, particular care must be exercised in the application of vapor fixing techniques in the preparation of animated cartoon eels.

The principal object of the present invention is to improve the method of vapor fixing xerographic powder images whereby controlled amounts of solvent vapor are applied to the support surface on which the powder images are formed to attain optimum vapor fusing. A further object of the invention is to improve the method of vapor fixing of xerographic powder images to prevent underfixing or overfixing of the powder images, and to minimize vapor dragout. A further object of the invention is to improve vapor fixing techniques for xerographic powder images to effect precise quantative control of the solvent vapor appiied to a powder image. A further object of the invention is to minimize solvent loss during vapor fixing.

These and other objects of the invention are attained in accordance with the method of the invention by generating at atmosphere of vapor of a solvent for the resin component of a xerographic powder image in a vapor chamber, superposing the vapor chamber over a powder image formed on a support surface, the vapor chamber and support surface being maintained in substantially vapor-tight relation, momentarily exposing the powder image to the vapor atmosphere of the chamber thereby to allow solvent vapor to penetrate into and tackify or soften the powder image to the point of adhesiveness, and removing the vapor chamber from superposed relation with the support surface to expose the powder image to ambient air thereby to allow the solvent in the image to evaporate and leave a fixed resin image on the support surface.

An apparatus for carrying out the foregoing method is disclosed in my above-cited copending application and includes the combination of a vapor chamber having integrally connected top and side walls and a removable bottom wall, a reservoir for resin solvent supported in the chamber, a wicklike element secured in spaced relation to the inner surface of the top wall of the chamber and extending into the solvent reservoir, and a peripheral gasket member secured to the bottom of the vapor chamber for forming substantially vapor-tight seal between the vapor chamber and a support surface.

The term tackified and the several variant forms thereof used throughout this specification are employed to define the condition of the powder particles of a xerographic powder image when treated in a manner such that the individual particles soften and coalesce and in which state they become sticky and readily adhere to other surfaces. Although this condition necessarily requires a flowing together of the particles to effect a thorough fusion thereof, it is to be understood that the extent of such flowing is not sufiicient to extend beyond the boundary of the pattern in which the particles are formed.

A form of apparatus for carrying out the method of the invention is shown in the accompanying drawings, in which:

FIGS. 1 and 2 are isometric views of a xerographic powder image fixing apparatus shown in its inoperative and operative positions, respectively; and

FIGS. 3 and 4 are sectional views of the vapor fusing apparatus taken along the lines 33 and 44, respectively, of FIG. 2.

In the form of apparatus shown in the drawings, there is provided a vapor chamber 16 that is formed of side rails 11 and 12, front rail 13, and a lateral rear compartment member 14 that are integrally connected at their ends to form a rectangular frame. Side rails 11 and 12 and front rail 13 are channel-shaped members having turned-over upper edge portions that cooperate with a similar turned-over portion on rear compartment member 14 to form a continuous support for a rectangular top wall member 15 that is secured thereto by screws 16. A rectangular gasket 17 is placed between top wall 15 and the rectangular frame in order to form a vapor-tight seal therebetween. For providing a removable bottom wall for vapor chamber 10, longitudinal, formed extrusion members 19 and 2% are secured to the under sides of rail members 11 and 12, respectively. Each of the members 19 and 20 is provided with a shoulder portion 21 which, together with the lower edges of rails 11 and 12, form lonigtudinal grooves to accommodate the side edges of a rectangular bottom plate 22. A lateral, formed extrusion member 23 (see FIG. 3) is secured to the forward edge of the underside of rear compartment member 14 and is provided with a shoulder portion 24 to accommodate the leading edge of bottom plate 22 when it is moved to its extreme rearmost position. Another lateral, formed extrusion member 25 is secured at each end to the under side of front rail member 13, and is spaced therefrom to form a slot-like opening to permit the insertion and withdrawal of bottom plate 22. If desired, a resiliently urged felt seal (not shown) may be provided on the lower edge of front rail member 13, in the manner commonly employed in the construction of photographic cassettes, to provide a seal between the lower edge of rail member 13 and lateral member 25 when bottom plate 22 is withdrawn.

For mounting vapor chamber it) with respect to a work surface, side rails 11 and 12 are provided with trunnions 27. Each trunnion is fixed on its respective side rail and is provided with a shouldered extension 28 that extends into a ball bearing 25 that is seated in a mounting bracket 30 that may be secured on a suitable work table or other support 31. A lock nut 32 is provided to bear against the outer face of bearing 29 and retain it in position in bracket 30. Fixed to the outer end of extension 28 is an arm 33 that extends upwardly and is provided with a horizontal pin 34 that is connected by a spring 35 to a corresponding pin (not shown) mounted on the lower end of bracket 30. By this arrangement, vapor chamber 16 is pivotally mounted for rocking movement about the axis of trunnions 27, whereby the chamber may be lowered to a substantially horizontal or operative position, as shown in FIG. 2, or raised to an inclined or inoperative position, as shown in FIG. I. In either position, the vapor chamber is resiliently urged to its limit of movement by the toggle action exercised by spring 35. A counterweight 37 secured at the rear of compartment member 14 serves to balance the weight of the forward portion of the vapor chamber to facilitate manual operation.

For forming an atmosphere of solvent vapor within chamber 10, the apparatus includes a vapor generating mechanism comprising a slotted tubular reservoir 40 that is provided with end caps 41 to form a liquid-tight container, and is secured to the bottom portion of rear compartment member 14 by fasteners 42. Preferably, reservoir it? is positioned so that its longitudinal axis is aligned with the pivotal axis of the vapor chamber to minimize the movement of resin solvent 43 within the reservoir. An upwardly extending tubular connection 44 is provided for filling reservoir 40, and a drainage hole is provided at the bottom of the reservoir whereby it may be emptied by removing a cap screw 45.

For withdrawing resin solvent from reservoir 4% the apparatus includes a wicklike member 47 that may be made of felt or similar porous material and is substantially rectangular in form and coterminous with the area of the opening formed by side rails 11 and 12, front rail 13, and the forward edge of rear compartment member 14. Wick member 4-7 is supported by a relatively stiff screen or grid member 48 which, in turn, is supported on brackets 49 that are fixed on the inner faces of side rails 11 and 12.

For forming a vapor-tight seal with a support surface placed on work table 31, formed extrusion members 19, 20, 23, and 25, are provided with grooved portions on their lower faces for seating a rubber or similar resilient gasket member 50. Gasket member 50 thus extends com pletely around the peripheral edge of the opening formed by side rails 11 and 12, front rail 13, and rear compartment member 14, and is so arranged that it seats squarely on work table 31 when vapor chamber is moved to its lowermost position.

By the arrangement thus described it is apparent that resin solvent placed in reservoir 40 is drawn upwardly into wick member 47 and evaporates therefrom in the atmosphere of the chamber to form a saturated atmosphere of solvent vapor within the chamber. When bottom plate 22 is in closed position (as shown in FIG. 1), the solvent vapor reaches a saturated condition as determined by the ambient temperature, thereby providing a substantially fixed amount of available solvent vapor.

When a cel or other support surface having a xerographic powder image formed thereon is to be fixed, it is placed on the surface of work table 31 immediately beneath the frame of the vapor chamber. The vapor chamber is then manually lowered to press gasket member 50 into surface contact with the edge of the cel or support surface. Bottom plate 22 is then removed momentarily to expose the powder image to the vapor in the chamber. This relationship is maintained for sulficient time period to effect complete tackification of the powder particles of the image. This time period may be determined empirically in accordance with the size of the work sheet, the ambient temperature, and the amount and type of xerographic developing material that may be employed, and is usually in the range of from two to ten seconds when trichloroethylene or a similar solvent is used. At the end of the required time period, bottom plate 22 is reinserted to close the vapor chamber, and the vapor chamber is then raised to its uppermost position. This action exposes the tackified powder image to ambient air to permit the solvent to evaporate from the powder image and leave a fixed xerographic powder image on the cel. The closing of the chamber by plate 22 retains all unused solvent vapor within the chamber. As the chamber is raised to its uppermost position, Wick 47 is effective to disperse additional solvent vapor into the atmosphere of the chamber to replace that used in fixing the powder image. Thus, the only vapor that is lost to the atmosphere is that, that actually condenses to tackify the powder image and that which is confined between the surface of the cel and the bottom of plate 22 when the plate is restored to its closed position.

Thus, there has been described a xerographic powder image vapor fixing method whereby a metered quantity of vapor solvent may readily and conveniently be applied to a support surface on which a xerographic powder image is formed, thereby to attain optimum vapor fusing, to prevent underfixing or overfixing of powder images, and to minimize vapor dragout and solvent loss.

Obviously, a number of different types of instrumentalities and techniques may be employed in carrying out the method of the invention and widely difiering applications of the invention may be made without departing rom the scope thereof. Therefore, it is intended that all matter contained in the above description shall be considered as illustrative, and that the invention be limited only as defined in the appended claim.

What is claimed is:

The method of fixing a resin base powder image onto a support surface to which the powder image is loosely adhering,

comprising the steps of placing the powder image support surface in a stationary position on a work surface, generating an atmosphere of vapor of a solvent for the resin within the confines of a vapor chamber,

lowering the vapor chamber relative to the work surface to superpose the vapor chamber over the powder image on the support surface in substantially vaportight relation to ambient air,

opening the vapor chamber to cause solvent vapor therein to flow into surface contact with the support surface, maintaining the vapor chamber superposed on the support surface in substantially vapor-tight relation for a predetermined time period to allow solvent vapor to penetrate into and soften the powder image on the support surface to the point of adhesiveness,

closing the vapor chamber to limit the quantity of solvent vapor applied to the support surface,

and removing the vapor chamber from superposed relation with the support surface to expose the powder image to ambient air, thereby to allow the solvent in the image to evaporate and leave a fixed resin image on the support surface.

References Cited in the file of this patent UNITED STATES PATENTS 281,201 Oberle July 10, 1883 2,684,301 Mayo July 20, 1954 2,776,907 Carlson Jan. 8, 1957 2,817,277 Bogdonoif Dec. 24, 1957 3,049,810 lwerks Aug. 21, 1962 

